The ultimate goal of the proposed research is to clarify the relationships between plasma lipoproteins and atherosclerosis. We will approach this goal by investigating various physicochemical and enzymatic factors influencing the retention and accumulation of plasma lipoproteins and their lipids in arterial tissues by utilizing model systems. Since antiatherogenic effects on high density lipoproteins (HDL) may well be associated with the lecithin-cholesterol acyltransferase reaction, we intend to provide further information on the basic properties of human plasma lecithin-cholesterol acyltransferase, especially its physicochemical and immunochemical properties. We will study the roles of various apo-lipoproteins in the enzyme-lipoprotein interactions. We also intend to establish the method for enzyme purification from rat and swine sera in order to facilitate the study of the relationship between the enzymatic reaction and HDL metabolism in experimental animals. In addition, we will continue the study of the interactions of plasma lipoproteins with aortic connective tissue components, such as glycosaminoglycans, proteoglycans, elastin, and collagen. The effects, on these interactions, of the changes occurring in the surface and interior properties of the lipoproteins during their circulation and after their entry into the aorta will be systematically investigated.